1. Field of the Invention
The present invention relates to a method of etching a magnetoresistive (MR) film by using a plurality of hard masks.
2. Related Background Art
A magnetic head sensor has a magnetoresistive film whose resistance value changes in response to external magnetic fields. The magnetoresistive film has a magnetosensitive layer (free layer), while domain control films (bias layers) magnetically connected to the free layer are provided on both end parts in the track width direction of the free layer in order to control the direction of magnetization of the free layer. When manufacturing the magnetic head sensor, the magnetoresistive film formed on the substrate is etched with a mask. The mask is formed on a region corresponding to a track width of the magnetoresistive film, so that the area on the outside of this region is etched.
As the recording density of hard disk drives has been increasing, magnetoresistive films have been required to narrow their track width. However, no magnetoresistive film having such a narrow track width as to be employable in next-generation magnetic head sensors has been found yet.
A conventional magnetoresistive film etching technique using a mask has been described in Japanese Patent Application Laid-Open No. 2002-214799, for example. Techniques for etching various kinds of wiring with masks are described in Japanese Patent Application Laid-Open Nos. 2007-81383, HEI 10-49832, and HEI 7-161711, for example.